Flush latch



' J. E. HOGAN May 19, 1953 FLUSH LATCH Filed July 2, 1949 INVENTOR. Jo/w .5. HOGAN BY 6 ams INN- Patented May 19, 1953 FLUSH LATCH John E. Hogan, Los Angeles, Calif., assignor to Clark Hartwell and Eleanor M. Hartwell, copartners doing business as Hartwell Aviation Supply Company, Los Angeles, Calif.

Application July 2, 1949, Serial No. 102,893

3 Claims.

My invention relates to flush latches and more particularly to latches to be used on airplanes to hold inspection plates, access panels or the like. Included in the objects of my invention are:

First, to provide a flush latch which is an improvement on the latch assembly disclosed in the co-pending application of Theodore H. Beck et al., Serial No. 588,436, filed April 16, 1945, issued July 19, 1949, Patent Number 2,476,286.

Second, to provide a flush latch which is particularly suitable for use on airplanes designed for extremely high speed, and under conditions wherein high loads and extreme temperatures are encountered.

Third, to provide a flush latch which incorporates a novel spring construction wherein a single spring unit retains all parts of the latch in their operating positions.

Fourth, to provide a flush latch which although capable of withstanding extreme conditions, is easily released or latched without the use of tools.

With the above and other objects in view as may appear hereinafter, reference is made to the accompanying drawings in which:

Fig. 1 is an elevational view of my flush latch, taken from the inside of the structure on which it is mounted.

Fig. 2 is a sectional view from 2--2 of Fi 1, showing the latch in a secured position.

Fig. 3 is a similar longitudinal figure showing the latch in its released position, and,

Fig. 4 is a reduced fragmentary plan view of the latch taken from the outside of the structure in which it is mounted.

My flush latch i intended to hold an inspection plate or similar device, designated I, in a flush position over an opening in a structure 2 of sheet material. The surrounding structure is preferably provided with a recessed shoulder 3, to facilitate flush mounting of the inspection plate. The inspection plate is provided with one or more T-key slots 4 disposed perpendicular to the margin thereof.

The flush latch includes a mounting plate or bracket II, formed of sheet material. The mounting plate is divided to form two side flanges I2 by means of a longitudinal slot extending the length of the mounting plate except for a narrow web I3.

A portion of the material removed to form the slot, is bent at right angles to the side flanges I2 to form an inwardly extending pair of latch lever bearing ears or lugs I4 and similar keeper bearing ears or lugs I5. The latch lever ears I4 are disposed adjacent to the end of the plate remote from the web I3, and are connected by a latch lever journal pin I 6 which journals a latch lever I1 intermediate to its ends. The latch lever is formed of sheet material or casting and is channel shaped in cross-section. The latch lever includes an arm I8 the surface of which is oifset inwardly or outwardly from the normal surface of the lever so as to underlie a margin of the surrounding structure 2.-

The other arm I9, of the latch lever I I is flush, that is, it is intended to occupy a position when closed, flush with the surface of the panel or inspection plate I. The extended end of the arm I9 is provided with an inwardly ofiset lip 20. The extremity of the arm is doubled backward to form a cam face 2| extending in angular relation with the outer surface of the arm.

The bearing lugs I5 are spaced slightly greater than the bearing lugs I 4 and are disposed opposite the cross portion of the T-slot, in the inspection plate. The bearing lugs I5 are connected by a journal pin 22 which journals a keeper lever 23. The keeper lever or trigger 23 is likewise channel shaped in cross-section and of appropriate width to set into the cross portion of the key slot. The face of the keeper lever is, when in its closed position, flush with the arm I9 of the latch lever. The end of the keeper lever adjacent to the latch lever is directly under the journal pin 22 when the latch is closed and is adapted to overlie the offset tip 20 of the latch lever I'I. Bv this arrangement, outward pressure of the tip 20 does not produce any turning movement on the keeper lever 23. The cam face 2I of the latch lever I! is. disposed at such an angle that inward pressure of the cam face against the adjacent end of the keeper lever during movement of the latch lever towards its closed portion may produce sufficient turning movement on the keeper lever to tilt the keeper lever clear.

The extended end of the keeper lever or trigger 23 is offset as indicated by 24 to fit under and bear against the web I3 when the keeper lever is in its closed position.

A special spring member 3| is provided. The spring member is formed from a length of wire doubled upon itself to form in succession a loop 32 adapted to bear against the keeper lever 23; a pair of coaxial coils 33 looped about the journal pin 22, connecting members 34 joined to a second pair of coaxial coils 35 adapted to fit the latch lever journal pin I6, and a pair of spring arms 36 inturned at their extremities and extending under the connecting members 3!, to bear against the latch lever I1 adjacent its offset tip 20.

It should be noted that the loop 32 may in effect a. be split or cut in two so that a righ and a "left spring unit are thus formed, that is, the loop 32 may be formed similarly to the spring arms 36. This arrangement functions no differently than the construction shown, but may reduce the cost of manufacture of the spring memher.

The spring member exerts at all times a force tending to hold the keeper lever 23 against the web I3, and urge the offset tip 26 of the latch lever I! in a direction outwardly from the journal pin 22. That is, both levers are urged in a counterclockwise direction as viewed in Figures 2 and 3.

By varying the size of wire from which the spring member or members 35 are formed, the force require to effect unlatching may be varied. This is of considerable practical importance, for in the use of my latch in airplanes the conditions of service vary, and in some installations the external pressures may be quite high. A variation in spring, strength made possible by my specific spring member or members is much greater than would be the case if other types of springs, such as coil springs, were used.

In order to prevent excessive loading of the spring 3!. one of the lugs i5 is provided with a stop 31 which overlies a side flange of the lever 23, so as to engage the lever when moved to the dotted line position shown in Figure 3.

Operation of the flush latch is follows: To release the latch, the keeper lever 23 pressed inwardly near its extremity adjacent to the web 13. This rotates the lever clockwise to move the lever clear of the offset tip 20, thereby permitting the spring to rotate the latch lever in a counter clockwise direction, that is, from the position shown in Figure 2, to the position shown Figure 3. To reset the latch, it is merely necessary to rotate the latch lever against the force of the spring 3! until the cam 2% has deflected the keeper lever around the oiTset tip 20;

It should be observed that the construction illustrated and the arrangement of the spring enable the flush latch to be built of relatively heavy gage material. This is of increasing importance particularly for applications of the latch to high speed aircraft. This is indicated by the fact that my flush latch has proved highly successful in actual use in super-sonic airplanes.

Having fully described my invention, it is to be understood that I do not wish to be limited to the details herein set forth, but my invention is of the full scope of the appended claims.

I claim:

1. A flush latch structure, comprising: a mounting plate including coplanar side flanges, a longitudinal slot and pairs of journal lugs bordering said slot; journal pins connecting said pairs of ournal lugs; tandem disposed levers each of channel cross section pivoted within said slot on said pins between said journal lugs and adapted to occupy a coplanar closed position and an angular open position; and a wire spring unit including at least a pair of helical coils joined by a connecting link, and spring arms extending beyond said coils, said coils adapted to fit said pins, one of said arms engaging one of said levers to urge it to its closed position, the other of said arms engaging the other of said levers to urge it to its angular position.

2. A flush latch structure wherein a pair of levers are disposed in tandem relation and journalled on parallel fulcrum pins, said levers being movable between a coplanar closed position and an angular open position, the combination of; a wire spring unit including at least a pair of helical coils joined by a connecting link, and spring arms extending beyond said coils, said coils adapted to fit said pins, one of said arms engaging one of said levers to urge it to its closed position, the other of said arms engaging the other of said levers to urge it to its angular position.

3. A flush latch structure, comprising: a pair of levers disposed in tandem relation; mounting means including a mounting plate and parallel disposed journal pins for said levers adapted to permit pivotal movement between a coplanar closed position and an angular open position; and. a wire spring unit including at least a pair of helical coils joined by a connecting link, and spring arms extending beyond said coils, said coils adapted to fit said pins, one of said arms engaging one of said levers to urge it to its closed position, the other of said arms engaging the other of said levers to urge it to its angular position.

JOHN E. HOGAN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,337,531 Stockton Dec. 21, 1943 2,424,962 Best Aug. 5, 1947 2,461,893 Paxton Feb. 8, 1949 2,476,268 Beck et al. July 19, 1949 

